1. Field of the Invention
This invention relates to mechanical mountings for lens systems, among others, zoom lens systems, and more particularly to a mechanical mounting for a zoom lens operable with the selection of the manual and automatic focusing modes.
2. Description of the Prior Art
Many zoom lenses are now available in the camera market, and new zoom lenses are being proposed one after another. For the zoom lenses, on consideration of their operating aspect, there are two types of mounting mechanisms, one of which makes use of a focusing actuator and a zooming actuator as arranged to be operable independently of each other, or which may be called "two-actuator operating" form, and the other of which has the focusing actuator and the zooming actuator to be served by one and the same member, as, for example, the slide movement of the single member effects zooming and its rotative movement effects focusing, or which may be called "single-actuator operating" form. These two forms each have one merit and one demerit and, therefore, it is of importance to make an appropriate choice of which is suited for the given optical system and the required performance of the lens mounting.
Also, recently there has been proposed in the field of photographic engineering so-called automatic focusing apparatus in which the object distance is measured and the objective lens (focusing member) is automatically moved to an in-focus position. With this automatic focusing apparatus used in a single lens reflex camera having the aforesaid two-actuator operating type lens mounting so that the position of the focusing member of the zoom objective is automatically adjusted, when to shoot, the photographer needs only to actuate the zoom ring for optional focal length settings. This allows for the photographer to concentrate his all nerves on the composition of a picture and to obtain photographs as he has intended. And, this automatic focusing provision made at the zoom lens mounting and particularly the aforesaid two-actuator operating type zoom lens mounting gives an advantage that whilst the characteristic features of the two-actuator operating type zoom lens mounting, for example, the fact that the operating mechanism of the lens mounting is unnecessarily made much complicated, and the merit that the mistaking actuation as in the single-actuator operating type is avoidable, are preserved, the convenience, easiness and quick management characteristic of the single-actuator operating type are additionally acquired.